1. Field of the Invention
This invention concerns valve operation indicators and more particularly electrically operated valve indicators.
2. Description of the Prior Art
Filtering units of the sort adapted to filtering liquids such as lubricating oil or fuels for engines and other machines typically include a bypass arrangement which provides for flow of the lubricating oil or fuel without going through the filter elements if the filter becomes so clogged as to reduce the flow below safe levels. This bypass arrangement typically includes a poppet or other type valve located in a bypass flow passage and biased so as to be normally closed, with a pressure build up created by a clogged filter causing the valve to open.
It has long been recognized that it would be desirable to provide some means of indicating a bypass flow condition of the filter, since dirty oil or fuel allowed to circulate to the engine greatly increasing engine wear. Such means typically took the form of a switch or a probe mechanically operated to control an indicator, but this involved wear of the switch, complicated adjustments to reset the switch as well as maintenance problems.
To avoid such problems it has heretofore been proposed to provide appropriate connections so as to convert the valve itself and cause it to perform the function of a switch in an indicator circuit in which a current flow path is formed through the valve and the valve seat. Such an arrangement is shown in U.S. Pat. No. 3,644,915.
However, such an arrangement includes a metal-to-metal seal between the valve and valve seat, in order to insure sufficient conductivity to operate the indicator circuit, which is expensive to manufacture and is not entirely reliable since proper seating may not occur.
It is, therefore, an object of the present invention to provide an integral valve switch in which positive sealing of the valve is achieved while the valve construction is kept simple and economical to produce.
It is a further object of this invention to provide a filter bypass valve switch which permits the use of a rubber valve body or seat, yet at the same time provide a path for conducting current flow through the bypass valve switch when the valve is closed.